If $x \bigtriangledown y = 2x-7$ and $x \otimes y = x(y-6)$, find $-1 \bigtriangledown (3 \otimes 5)$.
Solution: We don't need to find $3 \otimes 5$ because $x \bigtriangledown y$ depends only on the left operand. Find $-1 \bigtriangledown y$ $ -1 \bigtriangledown y = (2)(-1)-7$ $ \hphantom{-1 \bigtriangledown y} = -9$.